Signed by U.S. President Ronald Reagan and Soviet leader Mikhail Gorbachev in 1987, the Intermediate-Range Nuclear Forces (INF) Treaty is the only Cold War-era U.S.-Soviet arms control agreement that remains in force today. After the collapse of the Soviet Union in 1991, the United States sustained the INF Treaty with the Russian Federation and some other successor states.

The treaty was thrown into doubt in late 2018, when President Donald J. Trump said the United States would withdraw in response to many years of Russian violations. Moscow said the Trump administration had no evidence to corroborate the allegations. Some U.S. allies have warned a dissolution of the treaty would undermine European security.

What is the INF Treaty?

The former Soviet states that possessed nuclear weapons—Russia, Ukraine, Belarus, and Kazakhstan—participate in the INF Treaty with the United States. It required countries to destroy their stockpiles of ground-launched ballistic and cruise missiles with ranges between 500 and 5,500 kilometers. The treaty, which covers both nuclear and conventionally armed missiles, also prohibits signatories from possessing, producing, and flight-testing these kinds of missiles. It was the first agreement of its kind to reduce nuclear missile stocks instead of merely establishing a limit on arsenals. While the treaty required the elimination of missile bodies and launchers, it did not result in the elimination of nuclear warheads.

After the treaty entered into force in 1988, the United States and Soviet Union dismantled and destroyed about 800 and 1,800 missiles, respectively, along with related equipment such as launchers. A pillar of the treaty was a rigorous verification regime, including on-site inspection, which allowed parties to physically confirm the other’s implementation. Both sides came into full compliance in the summer of 1991, months before the dissolution of the Soviet Union, by completely eliminating the systems covered by the treaty. On-site inspection activity ended in 2001, in accordance with the treaty.

The treaty also established a forum known as the Special Verification Commission for parties to address and resolve compliance concerns. It has met thirty times, with the most recent meetings taking place in November 2016 and December 2017. (The most recent meeting before 2016 took place in October 2003.)

What is the state of INF Treaty compliance today?

In recent years, both the United States and Russia have alleged the other has violated the INF Treaty, and many defense analysts have said that the thirty-year-old treaty is in danger of unraveling. That outcome seemed more likely in October 2018, when President Trump said he would pull the United States out at an unspecified date, claiming that Russia had been “violating it for many years.” Moscow said the United States had no grounds for the decision, which it called “a very dangerous step.”

These allegations have accompanied a general decline in bilateral ties since Russia’s annexation of Crimea in 2014 and its alleged interference in the 2016 U.S. presidential election.

In 2014, the U.S. Department of State said Russia violated its obligation not to “possess, produce, or flight-test” missiles prohibited by the treaty, although officials did not provide details as to the nature of the alleged violation. In December 2017, the U.S. State Department offered specifics, identifying a system the Russian military calls the 9M729, an extended-range version of the Iskander K, which is a short-range cruise missile that is compliant with the INF Treaty. The United States alleges the 9M729 violates the agreement.

Russia, for its part, has rejected these claims and alleged that the United States has itself violated the INF Treaty by deploying a component of a missile defense system—the Mark 41 Vertical Launch System (VLS)—that is capable of launching offensive missiles. It also claims the United States has used banned missiles in missile defense tests and that some U.S. armed drones are effectively banned cruise missiles.

U.S. officials deny these allegations. Regarding the VLS, they note that the text of the INF Treaty allows systems designed solely for intercepting “objects not located on the surface of the earth.” This VLS is part of missile defense systems the United States has deployed at sea and in Europe to protect allied countries from limited missile attacks by regional powers such as Iran. However, Russia has long questioned U.S. motives, and it says VLS systems on U.S. warships can launch both offensive cruise missiles and missile defense interceptors. In December 2017, the U.S. State Department rebutted each Russian allegation of U.S. violations of the INF Treaty.

Do Russia’s alleged violations alter the strategic environment?

Several U.S. military leaders have said that Russia’s alleged violations of the INF Treaty place allied forces in jeopardy. Testifying before the U.S. Congress in March 2017, Vice Chairman of the Joint Chiefs of Staff General Paul J. Selva noted that the treaty-violating system presents a risk to NATO facilities in Europe.

At the same time, General Curtis M. Scaparrotti, NATO’s supreme allied commander, added that [PDF] “Russia’s fielding of a conventional/nuclear dual-capable system that is prohibited under the INF Treaty creates a mismatch in escalatory options with the West.”

However, in July 2017 testimony, Selva told lawmakers that the treaty-violating system does not give Russia any particular military advantage in Europe “given the location of the specific missiles and deployment.”

The State Department’s 2017 Arms Control Compliance Report [PDF] said Washington was “consulting with allies to review a range of appropriate options should Russia persist in its violation.”

Where does the INF Treaty go from here?

The fate of the INF Treaty was highly uncertain following President Trump’s October announcement. The U.S. administration seems to have pivoted from its strategy of pursuing diplomacy with Moscow while taking “economic and military measures intended to induce the Russian Federation to return to compliance.” Military options included the research and development of conventional ground-launched intermediate-range missile systems, which the administration said would not violate the treaty. Moreover, in its inaugural Nuclear Posture Review, released in February 2018, the Trump administration proposed development of a new nuclear-armed sea-launched cruise missile, which U.S. defense leaders suggested might entice Russia to come back into compliance.

Arms control advocates recommend that the United States and Russia continue to use the Special Verification Commission to resolve outstanding disputes. Many experts and some U.S. allies in Europe caution that a breakdown of the INF Treaty would feed bilateral distrust and could precipitate the demise of other important nuclear arms treaties, such as the New Start Treaty, which is up for renewal in 2021. German Foreign Minister Heiko Maas called Trump's decision “regrettable” and said the INF Treaty is of tremendous importance to Europe, while UK Defense Secretary Gavin Williamson blamed Russia for the U.S. withdrawal and said his government stood “resolute” with the United States.

How does China factor into the INF debate?

In recent years both the United States and Russia have become more wary of China’s military capabilities. China’s growing nuclear and conventional missile inventory is mostly composed of systems in the INF Treaty-prohibited range of 500 to 5,500 kilometers.

Harry Harris, former chief of U.S. Pacific Command, recommended in April 2017 testimony that the United States renegotiate the treaty with Russia because it limits its ability to “to counter Chinese and other countries’ cruise missiles, land-based missiles.” Russian military officials, too, have pointed to Russia’s perceived imbalance with China [PDF] as a factor that could lead to the eventual demise of the treaty.

Other observers have recommended that the United States seek to bring China into the INF Treaty or seek a separate, similar agreement with the country. However, China has expressed no interest in joining the INF Treaty, and experts are doubtful that it would consider participating in the future.